Field of the Invention
The present invention relates to a light source unit and a projector including this light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects a screen of a personal computer and a video image, as well as images based on image data which is stored on a memory card on to a screen. In recent years, as these projectors, there have been proposed projectors which employ laser diodes which consume less electric power and which have a long life and high luminance.
A light source optical unit and a projector which are disclosed in Japanese Unexamined Patent Publication No. 2015-184303 (JP-A-2015-184303) include a light source which emits light in a range of green wavelengths, a light source which emits light in a range of red wavelengths and a light source which emits light in a range of blue wavelengths. Light emitted from the individual light sources is incident on a microlens array having a plurality of lens cells which are arc-shaped convex lenses. Then, the light is collected by a collective lens to thereby be shone on to a display device which is made up of DMDs (Digital Micromirror Devices). The lens cells are formed as pairs of an entrance lens cell and an exit lens cell. The light source light that is emitted from the light sources to pass through and exit from the lens cells is shone on to the whole of the display device where the light is superposed on one another.
The light source light of the light source unit is spread and narrowed uniformly by the collective lenses and the like within the projector so that the light source light is adjusted to a desired shining width. Owing to this, in the event that the projection range of an image on a screen is rectangular, the overall shape of the display device becomes rectangular, and it is desirable that each lens cell of the microlens array also takes a rectangular shape that substantially coincides with the aspect ratio of the display device.
On the other hand, in the event that the lens cells each have long sides and short sides like a rectangle, in order to allow incident diffuse light to exit properly from the exit lens cells of the microlens array, it is necessary to limit the magnitude of the entrance angle of the incident diffuse light to a certain magnitude or smaller so as to match the width of the lens cells in the direction of the short side. Owing to this, it is necessary to reduce the diffuse angle of the diffuse plate, thereby making it difficult to make the light uniform.